`discriminator` keyword is being used improperly in the schema

[schristley]

I discovered this when using a JSON validator. We have a discriminator keyword on all of our objects, however its usage is not correct. It's meant to be used with oneOf where the propertyName in the discriminator indicates what property can be used to distinguish the appropriate object in the oneOf union.

Because we aren't using oneOf anywhere, we should essentially delete all of the discriminators.

[schristley]

@javh This is an easy fix, I can add to #674 if you agree.

[javh]

@schristley, works for me to add it to #674. Thanks!